feat(server): delegate_task to a linked environment#16719

fix(server): remote task followers read only their own task

fix(server): a remote task with no project there says how to bring one

fix(web,mobile): a task a linked environment runs shows under its parent

fix(server): a remote task refuses worktree isolation, and its failures keep the cause

fix(server): acknowledge only the matching remote stop generation

fix(server): stopping a parent stops a finished remote task's thread there

fix(server): a remote task waits for its thread's delegated work

fix(server): report the failed remote run's provider error

feat(server): delegate_task to a linked environment